Process for making polygon coke in coking chambers and coke so produced

ABSTRACT

A process for producing coke in polygonal shape in indirectly heated coke oven chambers which comprises applying to shaped pieces of fine-grained, including pelletized or briquetted, coal, an intimate mixture of coal and iron ore, both of fine grainsize, thereby forming a shell on said pieces before subjecting them to the coking operation. Preferably, the grain size of the coal and the iron ore are below 1 mm, the ratio of coal to iron ore in the shell 33% by weight: 67 percent by weight. The invention also comprises the polygonal coke made by the process.

[ 51 Apr. 3, 1973 United States Patent [1 1 Wenzel et a1.

2,127,632 8/1938 Najarian..,................................. 2,805,141 9/1957 Apull.... 2,411,873 12/1946 I 2,052,329

[54] PROCESS FOR MAKING POLYGON COKE IN COKING CHAMBERS AND COKE SO PRODUCED 8/1936 Wendeborn................................75/3

Heitmann et a1...........................75/3

....75/3 Price m t e n O S n a H 54 66 99 11 l/ 11 ll 69 31 93 6 33 .9f ko c l e z c u 3 n m d a0 H m e uh nfl W W. m en'- "-I I. 9 w" s r- 0 t n e V n 1 l 5 7 1 Aachen, Germany said Wenzel and Schenck, by said Gudenau Primary Examiner-Murray Katz [73] Assignee:

Assistant Examiner-William R. Trenor AttorneyMcGlew and Toren [22] Filed: Jan. 18, 1971 [21] Appl. No.: 107,231

ABSTRACT [30] Foreign Application Priority Data Apr. 14, 1970 Germany....................

A process for producing coke in polygonal shape in indirectly heated coke oven chambers which comprises applying to shaped pieces of fine-grained, including pelleti'zed or briquetted, coal, an intimate mixture of size, thereby forming a shell on said pieces before subjecting them to the coking operation. Preferably, the grain size of the coal and the iron ore are below 1 mm, the ratio of coal to iron ore in the shell 33% by weight: 67 percent by weight. The invention also comprises the polygonal coke made coal and iron ore, both of fine grainm H /0 4 4W 9/ M 1 0 m ,A 7 MCI 6 mm s 7.n. m2 "4 I "5 m7 M3 I m5 7 .1 M 4 5 .U N 5 l [51] Int. Cl............C21b 1/10, 1301] 2/12, C22b 1/14 [58] Field of Search 17/46, 100 A, 100 B; 44/6, 44/10, 14; 75/3, 4, 42; 201/5 References Cited UNITED STATES PATENTS by the process.

2 Claims, 2 Drawing Figures I Von PATENTEnAPRs I975 F l G. 2

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ATTORNEYS PROCESS FOR MAKING POLYGON COKE IN COKING CHAMBERS AND COKE SO PRODUCED SUMMARY OF THE INVENTION The present invention relates to a process for making polygon coke in heated chambers from pieces of coal.

In a known process (US. patent application, Ser. No. 65,935 filed Aug. 21, 1970 it has been described that in conventional, indirectly heated coke oven chambers a coke of substantially even size may be obtained, where the pieces have the form of more or less regular polygons with distinctly planar shape. The resulting form is due to a special process of coke formation.

The special method leading to such formation consists in applying a thin outer layer of hematitic iron ore to pieces of coal to be coked which contains l8 to 38 percent by weight of volatile constituents or to pelletized or briquetted pieces of fine-grained coal, and then converting the pieces so prepared to a normal coking process; in a preferred embodiment of the process, the pieces to be coked are in the shape of shell pellets.

It is, however, a considerable drawback of the known coking process that on the one hand, large quantities of iron ore are necessary, in order to produce a sufficiently marked separating effect between the individual polygons after the coke has been removed from the GENERAL DESCRIPTION OF THE INVENTION structures 5 coated by shells 6. The interstices have dischamber and that, on the other hand, the layers of iron ore on the pieces of coke incur the risk of an early wearing away of the chamber walls. With normal coal for coking, i.e. a coal having a mean content of about 24 percent by weight of volatile constituents, and with pieces of coke intended to have the size of about'40-60 mm, good separating effects could only be accomplished when more than 10 percent of ore were pelletized onto the pieces.

It is an object of the present invention to provide a process which is free from the drawbacks of the known method in the preparation of polygon coke.

It is another object of the invention to provide a process which leads to satisfactory pieces of polygonal coke without the use of the large amounts of iron ore hitherto necessary for the separating effect.

Other objects and advantages of the process according to the invention will become apparent from the following detailed description and the accompanying drawings.

The invention is based on the surprising discovery that it is possible to produce polygon coke when using much smaller quantities of iron ore and yet have the desired separating effect at the surface between the individual pieces of coke, by using as separating layers not pure iron ore, as up to now, but by employing a mixture of fine coal and fine ore; it is an added advantage that the fine coal used in the mix can be the same, as a rule, as the one from which the coke is to be produced.

In the accompanying drawing, the structure of the polygon coke is schematically illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows, in section, a fragment of a filling for a coke oven chamber as introduced into a chamber; and

FIG. 2 illustrates the filling after coking according to the invention has taken place.

appeared.

In the following example, the process of the invention will be described in greater detail, but it should be understood that the example is given by way of illustration and not of limitation and that many changes in the details may be made without departing from the spirit of the invention.

EXAMPLE Coal used conventionally in the production of blast furnace coke and having a mean content of 24 percent by weight of volatile constituents, was comminuted to a grain size of below about 1 mm, which is the size coal usually assumes when being ground; about 15-25 percent had the size of 0.09 mm, about 60 percent from 0.1-0.2 mm. In order to shape pellets, water is added to the coal in an amount which is sufficient for starting the formation of pellets as soon as the coal particles are placed in a pelletizing dish or drum. This amount of water is slightly below the one at which a paste would form; about 8 percent by weight is a good quantity for the initial wetting of the coal. As the dish or drum rotates, pellets will be automatically formed. During this operation, more water is sprayed onto the pellets under formation, so that the final water content will be about 16 percent by weight. The pellets have a diameter of 30-40 mm.

Fine coal of the same type as described above having a mean grain size below 1 mm was intimately mixed with 65 percent by weight of hematite, likewise having a grain size below 1 mm. The ratio of coal ore in the mix was 33 67 by weight. Instead of pure hematite, a mixture of hematite with magnesite or with hydroxides will be satisfactory.

This mixture of coal and ore is then pelletized onto the coal pellets. This is done by using a rimmed pelletizing dish, the rim of which is filled with the mixture above described, and there the coal pellets are rolled until a shell is formed thereon of the mixture. In order to make the mixture adhere to the coal pellets, some more water is sprayed into the mixture. The amount of water should again be about 16% by weight of the orecoal mixture, so that the outer shell and the pellet coated thereby will have the same water content. The shell applied is of a thickness which will cause a content of iron ore to be 2.5 percent by weight distributed throughout the finished piece.

These shell pellets were then coked in a cylindrical chamber having a diameter of 38 cm and a height of 65 cm. About 2000 pellets of size 30-40 mm are charged at one time for coking. The temperature was maintained at about 1 C, the coking time 12 hours.

Grain analysis of the coke produced was as shown below:

O-Smm 5 H) mm 0.4% 30 mm l.2% 30 60 mm 68.5% over 60 mm 20.2% total l00.0%

In a rattler test the polygon coke with grain size above 40 mm was 88.4 percent at 100 drum revolutions.

it was further found that the bulk of the added ore, namely 75 percent, was contained in the smallest fraction with grain size below 5 mm. From there, a considerable amount of the iron used can be recovered by magnetic separation.

As seen from the example, the process of the invention permits to obtain polygon coke with very low ore contents and, moreover, it makes it possible to recover a large part of the added ore in the form of iron sponge. Since it is the main object of the process to make coke for blast furnaces, not even the iron or iron ore remaining in the coke is to be considered a loss. The iron in the polygon coke is obtained from the blast furnace as pig iron. Any iron contained in small coke pieces below 30 mm grain size is likewise recovered in a sintering plant and therefore not lost in the metallurgical process.

It is of great importance that by the admixture of large amounts of coal to the iron ore, before application of the shell, an effective protection of the chamber walls against attack by iron oxides is guaranteed.

What is claimed is:

1. Process for producing coke in more or less regular polygon shape, at least a major portion of which have a diameter of from about 40 to about 60 mm, which comprises (a) mixing together intimately fine grains of coal and hematite iron ore, said grains being below 1 mm, (b) applying the resultant mixture of fine grains of coal and iron ore to the outer surface of coal shapes which have been compacted of fine grains of coal and which contain from about 18 percent to about 38 percent by weight of volatile constituents, (c) thereafter heating the so-obtained shapes with coal-ore mixture coated thereon at coking temperature in an oven for a time sufficient to form substantially regular polygons of coke, and (d) removing and recovering the polygon shaped coke from the coking oven, the ratio of coal to iron ore in the mixture of step (b) being in the range of about 33 to 67 percent (by weight), and the thickness of the outer coating of said mixture on the coal shapes being such as to result in a weight of about 2.5 percent iron ore in the resultant polygonal coke.

2. Polygonal coke of more or less regular shape prepared according to the process of claim 1.

i i i 

2. Polygonal coke of more or less regular shape prepared according to the process of claim
 1. 